Merge pull request #6183 from LongPham7/Long_internship

Parsing and type-checking loop variants (aka ranking functions)

Author: SaswatPadhi

regression/contracts/invar_check_break_pass/main.c

@@ -6,7 +6,10 @@ int main()
   __CPROVER_assume(r >= 0);
 
   while(r > 0)
+    // clang-format off
     __CPROVER_loop_invariant(r >= 0)
+    __CPROVER_decreases(r)
+    // clang-format on
     {
       --r;
       if(r <= 1)

regression/contracts/invar_check_continue/main.c

@@ -6,7 +6,10 @@ int main()
   __CPROVER_assume(r >= 0);
 
   while(r > 0)
+    // clang-format off
     __CPROVER_loop_invariant(r >= 0)
+    __CPROVER_decreases(r)
+    // clang-format on
     {
       --r;
       if(r < 5)

regression/contracts/invar_check_large/main.c

@@ -22,9 +22,9 @@ int main()
   int l = 0;
   int r = 1;
   while(h > l)
+    // clang-format off
     __CPROVER_loop_invariant(
       // Turn off `clang-format` because it breaks the `==>` operator.
-      /* clang-format off */
       h >= l &&
       0 <= l && l < 5 &&
       0 <= h && h < 5 &&
@@ -44,8 +44,9 @@ int main()
       (2 > h ==> arr2 >= pivot) &&
       (3 > h ==> arr3 >= pivot) &&
       (4 > h ==> arr4 >= pivot)
-      /* clang-format on */
     )
+    __CPROVER_decreases(h - l)
+    // clang-format on
     {
       if(*(arr[h]) <= pivot && *(arr[l]) >= pivot)
       {

regression/contracts/invar_check_multiple_loops/main.c

@@ -6,12 +6,18 @@ int main()
   __CPROVER_assume(n > 0 && x == y);
 
   for(r = 0; r < n; ++r)
+    // clang-format off
     __CPROVER_loop_invariant(0 <= r && r <= n && x == y + r)
+    __CPROVER_decreases(n - r)
+    // clang-format on
     {
       x++;
     }
   while(r > 0)
+    // clang-format off
     __CPROVER_loop_invariant(r >= 0 && x == y + n + (n - r))
+    __CPROVER_decreases(r)
+    // clang-format on
     {
       y--;
       r--;

regression/contracts/invar_check_nested_loops/main.c

@@ -6,13 +6,19 @@ int main()
   __CPROVER_assume(n >= 0);
 
   for(int i = 0; i < n; ++i)
+    // clang-format off
     __CPROVER_loop_invariant(i <= n && s == i)
+    __CPROVER_decreases(n - i)
+    // clang-format on
     {
       int a, b;
       __CPROVER_assume(b >= 0 && a == b);
 
       while(a > 0)
+        // clang-format off
         __CPROVER_loop_invariant(a >= 0 && s == i + (b - a))
+        __CPROVER_decreases(a)
+        // clang-format on
         {
           s++;
           a--;

regression/contracts/invar_check_pointer_modifies-01/main.c

@@ -8,7 +8,10 @@ void main()
 
   unsigned i;
   while(i > 0)
+    // clang-format off
     __CPROVER_loop_invariant(*data == 42)
+    __CPROVER_decreases(i)
+    // clang-format on
     {
       *data = 42;
       i--;

regression/contracts/invar_check_pointer_modifies-02/main.c

@@ -10,7 +10,10 @@ void main()
 
   unsigned i;
   while(i > 0)
+    // clang-format off
     __CPROVER_loop_invariant(*data == 42)
+    __CPROVER_decreases(i)
+    // clang-format on
     {
       *data = 42;
       i--;

regression/contracts/invar_check_sufficiency/main.c

@@ -6,7 +6,10 @@ int main()
   __CPROVER_assume(r >= 0);
 
   while(r > 0)
+    // clang-format off
     __CPROVER_loop_invariant(r >= 0)
+    __CPROVER_decreases(r)
+    // clang-format on
     {
       --r;
     }

regression/contracts/invar_loop_constant_no_modify/main.c

@@ -6,7 +6,10 @@ int main()
   int s = 1;
   __CPROVER_assume(r >= 0);
   while(r > 0)
+    // clang-format off
     __CPROVER_loop_invariant(r >= 0)
+    __CPROVER_decreases(r)
+    // clang-format on
     {
       r--;
     }

regression/contracts/invar_loop_constant_pass/main.c

@@ -5,7 +5,10 @@ int main()
   int r, s = 1;
   __CPROVER_assume(r >= 0);
   while(r > 0)
+    // clang-format off
     __CPROVER_loop_invariant(r >= 0 && s == 1)
+    __CPROVER_decreases(r)
+    // clang-format on
     {
       s = 1;
       r--;